This invention relates generally to gas turbine engines, and more specifically to methods and apparatus for detecting fuel leakage from gas turbine engines installed inside an engine assembly compartment.
Gas turbine engines are used as a power source within a variety of applications. To protect the engine from the environment, and to shield a surrounding environment from the gas turbine engine, at least some known gas turbine engines are contained within an engine assembly compartment that includes an inlet area, an exhaust area, such as an extraction duct, and an engine area that extends between the inlet area and the exhaust area. For example in a power generation facility where the gas turbine engine is used as a power source for an electrical generator, the engine may be housed inside a compartment which facilitates reducing noise and heat generated during engine operation.
Within at least some known compartments, the inlet includes ducts to route ambient air from outside the compartment into the engine compartment for cooling the engine and compartment, and the outlet includes ducts to discharge heated air produced during operation of the engine.
Cooling requirements for a turbine may vary based on operational requirements of the engine, and, as such, at least some known turbine engines use a variable speed cooling fan to control the supply of cooling air channeled to the engine.
However, current regulatory codes may require that an engine control system provide an alarm to an operator and/or automatically stop the engine""s operation in an action known as a trip when fuel leakage from the engine within a compartment exceeds a pre-selected limit. At least some known engine assembly compartments may include a hazardous gas detector located in the extraction duct air stream to detect the presence of a fuel leak. A measured concentration at the detector may vary as the air flow rate through the compartment is varied due to the cooling requirements of the engine. For example, for a given leak rate, the measured concentration at the detector may increase as fan speed decreases due to dilution of the fuel in a lesser quantity of air. If a constant hazardous gas detector limit is used when operating at a reduced fan speed, an unnecessary trip of the engine may occur.
In one aspect, a method for detecting a fuel leak in a compartment is provided. The compartment includes at least one inlet and an exhaust outlet that is coupled in flow communication with the compartment and in flow communication with a fan. The method includes determining a fan speed, measuring a fuel leak gas concentration value, determining a fuel leak gas concentration limit value within the compartment based on the determined fan speed, comparing the measured fuel leak gas concentration value with the determined fuel leak gas concentration limit value, and generating at least one of an alarm signal and a trip signal based on the comparison.
In another aspect, a leak detection system for detecting a fuel leak in a compartment having an inlet and an extraction duct that is coupled in flow communication with the compartment and in flow communication with a fan is provided. The system includes at least one fuel leak detector, a software code segment programmed to determine a measured fuel leak gas concentration value based on an output signal from said at least one fuel leak detector, determine a fuel leak gas concentration limit value, compare the measured fuel leak gas concentration value with the determined fuel leak gas concentration limit value, and generate at least one of an alarm signal and a trip signal based on the comparison.